The LWF Blog

Fire Engineering Design and Risk Assessment – Sprinkler Installation Design – Part 35

March 1, 2018 11:07 am

In this Fire Engineering blog series for Architects and others involved in building design, LWF has been discussing planning for the installation of sprinkler systems and the risks which must be ascertained and taken into consideration. Once the basic design requirement is in place, the next step is to address the supply of water to the system. In part 35, the main points of water supplies will be considered.


A sprinkler system is only as effective and reliable as the water supply it is connected to. Water must be available in sufficient quantities and for a suitable duration when required. The supply of water to a sprinkler system must be reliable, have a good flow rate and come from a source where there is sufficient capacity to feed the system for the time it is calculated to need.


In high hazard situations, the water supply must be suitably high in flow rate and capacity and, of course, must be reliable.


A water supply can be classified under one of three designations: single supply, superior supply and duplicate supply. A light or ordinary hazard installation is suitable for any of the water designations. A high hazard risk would only work in cases where the water supply was superior or duplicate.


A single water supply would usually consist of:


 a town main fed from a single source


 a single automatic suction pump drawing from a suitable source


 a single automatic booster pump drawing from a town main fed from a single source.


A superior supply might be:


 a town main which is fed from more than one source, and from both ends which is not dependent upon a common trunk main


 two automatic suction pumps which draw from a suitable source


 two automatic booster pumps which draw from a town main as outlined in the first point of this section


 an elevated private reservoir


 a gravity tank


 a pressure tank (suitable only for light and ordinary hazard risks)


A duplicate supply would involve the use of two of the above-listed supplies, but in the UK is most commonly a full holding capacity water storage tank and duplicate fire pumps.


It may be the case that duplicate pumps are required and in such situations, each pump must have the capacity to fulfil the requirements by itself. Where two pumps are needed, each pump must have independent electricity supplies so that if one supply fails, the other pump will continue to work. It is often found that one pump may be supplied by electricity and one by diesel, to avoid the necessity of two separate electricity supplies. In cases where one pump would not be sufficient if the other was out of action, three pumps must be used, each of which must be capable of providing half of the required capacity of water.


In part 36 of this series, LWF will continue to look at the water supply to sprinkler systems and how height differential affects matters. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.


Lawrence Webster Forrest has been working with their clients for over 25 years to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact Peter Gyere on 020 8668 8663.


While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.



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